Synchronous motor



Jan. 3, 1933. H. P. SPARKES SYNCHRONOUS MOTOR Original Filed Nov. 5, 1920 INVENTOR Harry P .Sparkes.

WITNESSES:

ATToizm-zv Patented Jan. 3, 1933 UNITED STATES PATEiNT, OFFICE m 1. 5243113, or nnenwoon rnzx, rnmisvnvnivm, assrononro wnsrmc- 'nousn ELECTRIC a murncrumne oouranv, A conrons'rron or rnnivsvnvmm simcrmonoos moron Application filed November 5, 1920, Serial No. 421,882. Renewed December 17, 1929.

ing such characteristics that, when it becomes overloaded at synchronous speed, its torque is automatically increased to hold it in SYIIChI'ODiSDJ.

Another object of my invention is to rovide a motor, of the above indicated 0 aracter, thatshall 0 erate at a relatively low speed to adapt it or time-keeping purposes.

A further object of my invention is to pro: vide a motor, of the above indicated character, that shall be inexpensive to construct and efiective in its operation.

In practicing my invention I provide a magnetizabie core having spllt pole pieces and an ene gizing winding to produce a rotatingfield." The rotor of the motor comprises a non-xiragnetizable disk and a plural-v ity of magnetifzable pins disposed thereon; The shaft of the motor is adapted to he moved" longitudinally, as well as to turn. The nonmagnetizable armature operates, by reason of the eddy currents induced therein, as a short-circuited' secondary member of an induction motor having a good starting torque and tending to accelerate the motor almost to the ,full synchrpnous speed corresponding to the two-pole stator member. The magnetizable pins, on the other hand, develop substantially no tdrque except at a certain subsynchronous speed dependin upon the number of pins, and the effect 0 such operation is to tend to draw the motor into such subsynchronous speed and to prevent it from accelerating beyond such speed.

At starting,-the induction-motor torque of the non-magnetizable disk is practica ly the only torque, and the disk is disposed in a position of maximum" field intensityf When the critical sub-synchronous speed is reached, the magnetizable pins will be drawn into the position of maximum field intensity, and the motor will lock in step as a synchronous motor. When the magnetizable f the pins thus begins to decrease, the induction-motor torque of the disk will begin a ain to predominate, the disk will be brought into .better position within the influence of thefield, and its induction-motor torque will thus I be increased the better to assist the synchrofallingback out of step.

A motor of the above desi nated character, by reason of its relatively ow synchronous speed, is particularly adapted to indicate time, when connected to an alternating-curpins'are' within the field of maximum inv nous-motor torque to prevent the motor from rent system, the frequency of which is constant.

Figure 1 of the accompanying drawing is a side view of a motor embodying my inven tion, and Y ,Flg; 2 is a view, partially" in section and partially in end elevation, of the motor shown in Fig. 1. n

The motor 1, embodying my invention, comprises a nfagnetizable core 2 having split pole pieces 3 and 4 around portions of which are disposed closed-circuit conductors 5 and 6 to produce a rotating magnetizing field in an air'gap 7 between the pole pieces.

A magnetizing winding 8 is disposed around one leg 0 the core 2 for the purpose of energizing the same. Non-magnetizable plates 9 and 10 are disposed adjacent the core 2 and a-non-magnetizable supporting bracket llisiiis'posed adjacent the airgap 7. The bracket 11 supports a shaft 12 which is rotatably and longitudinally movable therein and has mounted thereon a non-magnetizable metal disk armature 13'havin a plurality of magnetizable pins 14 dispos in one face thereof.

The disk 13 is normally disposed in the position of the inaximum produced by the winding and the pins 14 arenormally disposed outside of the maximum field. The

disk 13, being non-polar and non-magnetizable, has a relatively high starting torque, but its torque decreases withan increase in speed. The magnetizable p'ns 14 have relat vely poor starting torque but relatively hlgh synchronous torque. Consequently the shaft .12 is started by reason of the disk 13 acting as the rotor of a h' h -torque induction motor, and the magnetiza 1e pins 14, are then drawn into a position in which they operate in a magnetic field of maximummtensity. In other words, the shaft 12 will move longitudinally until the disk13 occupies a posit1on adjacent-to the non-magnetizable plate 9 and the bracket 11 and is, therefore, out

I side of the effective field of the motor,while the pins 14, are in a field of maximum 9 strength. In this position, the motor, by reason of the large numbers of pins, will operate in sub-synchronism with the alternatingcurrent circuit to which the winding 8 is connected. Since the number of pins is large,

the speed will be'relatively low or sub-synchronous in accordance with-the number of pairs of pins employed relative to the number of pans of poles.

If the shaft 12, which is adapted to be .connected to Jclockhan or to drive devices which should be driven at a constant speed, becomes overloaded, it will tend to drop out of step and, when this occurs, the disk 13 will be drawn into the maximumfield, and the to ue will increase to hold the shaft 12 1n sync ronism. It will be understood that the disk '13 and the pins 14 do not co-operate 'under' normal synchronous operation but merely co-operate under starting and pullout conditions;

It must be borne inmind that the disk 13 must of necessit be a non-ma etizable' member in order t at it may assist t e pins 14 to maintain synchronism whenthey are overloaded and in order that a. plurality of'pins maydbe used to thus obtain a relatively low spw shown in an application by O. F. Rowe, Serial No. 557 ,294, filed April- 29, 1922,;and asiiigned to the Westinghouse Electric and anu'facturing Company. The claims to the common or generic subjects-matter of the two applications are in the said Rowe appli- 5 cation.

My invention is not limited to the specific structure illustrated, as it may-be variously modified without departing from the s irit and scope of the invention, as set fort 'in theappended claims.

I claim as my invention 1'. A selfstarting motor comprising means for producing a rotating magnetic field hav-' mgapulsating fluxj'c'o'mponent, a non-ma U5 invention is an improvement over that.

said. field to be rotated thereby, with a relatively strong starting torque and a plural-1" ity of magnetizahle pinsdisposed on the for producing a rotating magnetic field having a pulsating flux component, a non magnetizable disk armature normally located in said field to be rotated thereby with a U relatively strong starting torque, said armature and field-producing means being rela tively movable longitu inally, and a plurality of magnetizable pins mounted on-th'e armature andnormally removed from the maximum influence of said field but adapted to be attracted into the maximum influence of said field and to rotate in predetermined fixed relation to the field at a relatively low, or sub-synchronous, speed, the number of pins being large in comparison to the number of poles.

3. A self-starting alternating-current motor comprising means for producinga rotating magnetic field-having apulsatlng flux component, and an armature mounted for rotation and longitudinal displacement relative to said field-producing means;said armature comprising'a non-polar secondary member normally disposed in a strong portlon of the field for producing a good starting to us, and a longitudinally displaced polar mem comprising a. plurality of magnetic pole pie'ces adapted to be attracted into a strong portion of the field for causing said armature to rotate in predetermined fixed relation to dis laced polar member comprising a plurahty of magnetic pole pieces ada ted to be attracted into a strong portion 0 the field for' causing said armature to rotate in predetermined fixed relation to the field, the magnetic pole pieces of the armature being .more numerous than-the salient polar members of the field member and being adapted to cooperate with the split portions of said field polar members to operate the armature at asub-synchronous speed.-

5. A self-starting alternating-current motor comprising a field member avingsalient polar members having axially extending le disk armature'normally located in splits therein, means for producing a rotatmagneticfield in said field member, and

field member, said armature comprising a portion constituting an induction-motor secondary member tendin to accelerate said motor almost to full sync n'onous speed corresponding to the number of salient polar members of said field member, and a longi-. tudmally removed portion constituting a salient-pole synchronous-motor member havmg a relatively large number of salient poles adapted to lock into step with respect to the split portions of said field polar members at a definite sub-synchronous speed, said armature being normally biased to a position in which said induction-motor portion is m a strong magnetic field, and the magnetic attraction between said salient-pole portion and the field being. suflicient to displace said induction-motor portion into a weaker magnetic field during running conditions.-

6. In a motor, the combination with means for producing a rotating magnetic field have mg a pulsating flux component, of a composite armature comprising longitudinally displaced non-magnetic and magnetic .ele; ments effective, respectively, to operate the armature as an induction-motor armature and as an armature rotating in predetermined sub synchronous relation to the field.

7. In a motor, the combination with means for producing a rotatingmagnetic field having a pulsating flux component, of a com posite armature mounted for rotation and longitudinal movement relative to said field I means and comprising a non-magnetic element efiective to operate the armature as an induction-motor armature and a plurality of longitudinally removed magnetic elements effective to operate the armature in predetermined sub-synchronous relation to the field, said armature being normally biased to a osition in which said non-magnetic element 1s in a strong magnetic field, and the magnetic attraction between said magnetic elements and the field being suflicient to displace said non-magnetic element into a weaker magnetic field during running conditions.

8. A self-starting single-phase motor. comprising a bipolar field member, each pole Eiece thereof being split longitudinally and aving a shading coil on one of the split por tions, a single-phase coil for magnetizing said field member, and a composite armature comprising aportion including a non-magnetic element effective to produce torque as an induction-motor armature and a lon itudinally displaced portionincluding a plurality of ma etic elements efiective to lock into step wit res ct to the'split portions of said field pole pieces at 'a definite sub-synchronous s 9. A sel -starting single-phase motor compiece thereof being split longitudinally and havmg a shading coil on one of the split por tions, a single-phase coil for magnetizing said nous-motor member having a relatively large a number of salient poles adapted to look into step with respect to the split portions of said field pole pieces at a definite sub-synchro-a nous speed, said armature being normally biased to a position in which said inductionmotor member is in a strongmagnetic field, and the-magnetic attraction between said salient-pole member and the field being suflicient to displace said induction-motor memberinto a weaker magnetic field during running conditions.

10. A self-starting single-phase motor comprising a bipolar fie'ld' member, each pole piece thereof being split longitudinally and having a shading coil on one of the split por tions, a single-phase coil for magnetizing said field member, an armature mounted for rotation relative to said field member, said armature comprising means constituting an induction-motor secondary'member tendingto accelerate said motor almost to full blpolar synchronous speed, and longitudinally. displaced means constituting a salient-pole synclri'onous-motor member having a relatively large number of salient poles adapted to lock into ste with respect to the split portions of said eld pole pieces at a definite sub-synchronous speed, and means-for automatically strengthening the synchronizing effect of the salient-pole armature means at the expense of the induction-motor armature means when the pull-in torque of the salient-pole armature means begins to become efiective.

'11 A self-starting single-phase motor comprising a bipolar field member each pole piece thereof being split longitudinally and having a shading coil on one of the,spl1t p or-' tions, a single-phase coil for magnetlzing said field member, -an armature mounted for rotation relative to'said field member, said armature comprising means constituting an induction-motor secondary member tending .to accelerate said motor almost to full biprising a bipolar field member, each pole Qthe expense of the synchronizing effect of the salienb-polearmature means when the load increases to a point approaching thepullout value. 12. An induction motor operable at .a fixed 5 synchronizedspeed characterized by having a rotor structure comprising anon-magnetic secondary member and a pin-type reaction member aving a plurailty of pairs of ma'g- .netizable pins. a s "In testimony whereof, I- have hereunto subscribed my name this'22nd day of October HARRY P. SPARKES. 

